Mr Buyoya – who has seized power twice in the last three decades with the backing of the army – is respected diplomatic figure on the continent.

In the past he has reacted angrily to a suggestion that he may have been connected to Mr Ndadaye’s assassination, which took place four months after the country’s first democratic election. He has never issued a formal denial as he had not faced legal charges.

Image copyrightReutersImage caption Regional leaders are trying to ease tensions in Burundi so those who fled unrest in 2015 can return

The 69-year-old was involved in the peace process that ended the civil war and saw the election in 2005 of former Hutu rebel leader Pierre Nkurunziza as president.

The current peace negotiations surround the political unrest sparked by Mr Nkurunziza’s decision to run for a third term in office in 2015.

He was ultimately successful, but amid violent opposition protests and a failed coup attempt, hundreds of people died and many of the 400,000 who fled their homes remain in neighbouring countries.